Lepidoptera morphology - AbsoluteAstronomy.com

The external morphology of Lepidoptera is the physiological structure

Morphology (biology)

In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

of the bodies of insect

Insect

Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s belonging to the order Lepidoptera

Lepidoptera

Lepidoptera is a large order of insects that includes moths and butterflies . It is one of the most widespread and widely recognizable insect orders in the world, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...

, also known as butterflies

Butterfly

A butterfly is a mainly day-flying insect of the order Lepidoptera, which includes the butterflies and moths. Like other holometabolous insects, the butterfly's life cycle consists of four parts: egg, larva, pupa and adult. Most species are diurnal. Butterflies have large, often brightly coloured...

and moth

Moth

A moth is an insect closely related to the butterfly, both being of the order Lepidoptera. Moths form the majority of this order; there are thought to be 150,000 to 250,000 different species of moth , with thousands of species yet to be described...

s. Lepidoptera are distinguished from other orders principally by the presence of scales

Scale (Lepidoptera)

The presence of scales on the wings of Lepidoptera, comprising moths and butterflies, characterises this order of insects. The name is derived from Ancient Greek λεπίδος and πτερόν . The wings of Lepidoptera are minutely scaled, which feature gives the name to this order...

on the external parts of the body and appendages, especially the wings. Butterflies and moths vary in size from microlepidoptera

Microlepidoptera

Microlepidoptera is an artificial grouping of moth families, commonly known as the 'smaller moths' . These generally have a wingspan of under 20 mm, and are thus harder to identify by external phenotypic markings than macrolepidoptera...

only a few millimetres long, to conspicuous animals with a wingspan of many inches, such as the Monarch butterfly and Atlas moth. Comprising over 160,000 described species, the Lepidoptera show many variations of the basic body structure which have evolved to gain advantages in lifestyle and distribution.

Lepidopterans undergo complete metamorphosis

Metamorphosis

Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation...

, going through a four-stage life cycle

Biological life cycle

A life cycle is a period involving all different generations of a species succeeding each other through means of reproduction, whether through asexual reproduction or sexual reproduction...

: egg

Egg (biology)

An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...

; larva

Larva

A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...

or caterpillar

Caterpillar

Caterpillars are the larval form of members of the order Lepidoptera . They are mostly herbivorous in food habit, although some species are insectivorous. Caterpillars are voracious feeders and many of them are considered to be pests in agriculture...

; pupa

Pupa

A pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...

or chrysalis; and imago (plural: imagines)

Imago

In biology, the imago is the last stage of development of an insect, after the last ecdysis of an incomplete metamorphosis, or after emergence from the pupa where the metamorphosis is complete...

/ adult. The larvae – caterpillars – have a toughened (sclerotised

Sclerite

A sclerite is a hardened body part. The term is used in various branches of biology for various structures including hardened portions of sponges, but it is most commonly used for the hardened portions of arthropod exoskeletons....

) head capsule, chewing mouthparts

Insect mouthparts

Insects exhibit a range of mouthparts, adapted to particular modes of feeding. The earliest insects had chewing mouthparts...

, and a soft body, that may have hair-like or other projections, 3 pairs of true legs

Arthropod leg

The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments are of Latin origin, and may be confused with terms for bones: coxa , trochanter , femur, tibia, tarsus, ischium, metatarsus, carpus, dactylus ,...

, and up to 5 pairs of proleg

Proleg

A Proleg is the small fleshy, stub structure found on the ventral surface of the abdomen of most larval forms of insects of the order Lepidoptera, though they can also be found on other larval insects such as sawflies and a few types of flies....

s. Most caterpillars are herbivore

Herbivore

Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...

s, but a few are carnivore

Carnivore

A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...

s (some eat ants, aphids or other caterpillars) or detritivore

Detritivore

Detritivores, also known as detritophages or detritus feeders or detritus eaters or saprophages, are heterotrophs that obtain nutrients by consuming detritus . By doing so, they contribute to decomposition and the nutrient cycles...

s. Larvae are the feeding and growing stages and periodically undergo hormone-induced ecdysis

Ecdysis

Ecdysis is the moulting of the cuticula in many invertebrates. This process of moulting is the defining feature of the clade Ecdysozoa, comprising the arthropods, nematodes, velvet worms, horsehair worms, rotifers, tardigrades and Cephalorhyncha...

, developing further with each instar

Instar

An instar is a developmental stage of arthropods, such as insects, between each molt , until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, or...

, until they undergo the final larval–pupal moult. The larvae of many lepidopteran species will either make a spun casing of silk called a cocoon and pupate

Metamorphosis

inside it, or will pupate in a cell under the ground. In many butterflies, the pupa is suspended from a cremaster and is called a chrysalis.

The adult body has a hardened exoskeleton

Exoskeleton

An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...

, except for the abdomen which is less sclerotised. The head is shaped like a capsule with appendages arising from it. Adult mouthparts include a prominent proboscis

Proboscis

A proboscis is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In simpler terms, a proboscis is the straw-like mouth found in several varieties of species.-Etymology:...

formed from maxillary galeae, and are adapted for sucking nectar. Some species do not feed as adults, and may have reduced mouthparts, while others have them modified for piercing and suck blood or fruit juices. Mandibles are absent in all except the Micropterigidae

Micropterigidae

Micropterigoidea is the superfamily of "mandibulate archaic moths", all placed in the single family Micropterigidae, containing currently about 20 living genera. They are considered the most primitive extant lineage of Lepidoptera ....

which have chewing mouthparts. Adult Lepidoptera have two immobile, multi-faceted compound eyes, and only two simple eyes or ocelli, which may be reduced. The three segments of the thorax

Thorax (insect anatomy)

The thorax is the mid section of the insect body. It holds the head, legs, wings and abdomen. It is also called mesosoma in other arthropods....

are fused together. Antennae

Antenna (biology)

Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....

are prominent and besides the faculty of smell, act as olfactory radar, and also aid navigation, orientation and balance during flight. In moths, males frequently have more feathery antennae than females, for detecting the female pheromone

Pheromone

A pheromone is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting outside the body of the secreting individual to impact the behavior of the receiving individual...

s at a distance. There are two pairs of membranous

Biological membrane

A biological membrane or biomembrane is an enclosing or separatingmembrane that acts as a selective barrier, within or around a cell. It consists of a lipid bilayer with embedded proteins that may constitute close to 50% of membrane content...

wings

Insect wing

Insects are the only group of invertebrates known to have evolved flight. Insects possess some remarkable flight characteristics and abilities, still far superior to attempts by humans to replicate their capabilities. Even our understanding of the aerodynamics of flexible, flapping wings and how...

covered which arise from the metathoracic (middle) and mesothoracic (third) segments; they are usually completely covered by minute scales

Scale (Lepidoptera)

. The two wings on each side act as one by virtue of wing-locking mechanisms. In some groups, the females are flightless and have reduced wings. The abdomen has ten segments connected with movable inter-segmental membranes. The last segments of the abdomen form the external genitalia

Lepidoptera genitalia

The study of the genitalia of Lepidoptera is important for Lepidoptera taxonomy in addition to development, anatomy and natural history. The genitalia are complex and provide the basis for species discrimination in most families and also in family identification. The genitalia are attached onto the...

. The genitalia are complex and provide the basis for family identification and species discrimination.

The wings, head parts of thorax and abdomen of Lepidoptera are covered with minute scales, from which feature the order 'Lepidoptera' derives its names, the word "lepidos" in Ancient Greek

Ancient Greek

Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

meaning 'scale'. Most scales are lamellar (blade-like) and attached with a pedicel, while other forms my be hair-like or specialised as secondary sexual characteristics. The lumen, or surface of the lamella, has a complex structure. It gives colour either due to the pigment

Pigment

A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...

s contained within it or through its three-dimensional structure. Scales provide a number of functions, which include insulation

Thermal insulation

Thermal insulation is the reduction of the effects of the various processes of heat transfer between objects in thermal contact or in range of radiative influence. Heat transfer is the transfer of thermal energy between objects of differing temperature...

, thermoregulation

Thermoregulation

Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different...

and aiding gliding flight, amongst others, the most important of which is the large diversity of vivid or indistinct patterns they provide which help the organism protect itself by camouflage

Camouflage

Camouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...

, mimicry, and to seek mates.

External morphology

In common with other members of the superorder

Order (biology)

In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

Holometabola

Endopterygota

The Endopterygota, also known as Holometabola, are insects of the subclass Pterygota which go through distinctive larval, pupal, and adult stages. They undergo a radical metamorphosis, with the larval and adult stages differing considerably in their structure and behaviour...

, Lepidoptera undergo complete metamorphosis

Metamorphosis

, going through a four-stage life cycle: egg, larva / caterpillar, pupa / chrysalis, and imago (plural:imagines) / adult. The morphology of the lepidopteran adult and immature stages have been extensively studied. The North American Cecropia moth Hyalophora cecropia
Hyalophora cecropia
The Cecropia Moth is North America's largest native moth. It is a member of the Saturniidae family, or giant silk moths. Females with a wingspan of 160 mm or more have been documented. It is found as far west as the Rocky Mountains and north into the maritime provinces of Canada...

and the Polyphemus moth Antheraea polyphemus
Antheraea polyphemus
The Polyphemus Moth is a North American member of the family Saturniidae, the giant silk moths. It is a tan colored moth, with an average wingspan of 15 cm . The most notable feature of the moth is its large, purplish eyespots on its two hindwings...

(both saturniids

Saturniidae

The Saturniidae, commonly known as saturniids, are among the largest and most spectacular of the moths. They form a family of Lepidoptera, with an estimated 1,300 to 1,500 described species worldwide...

), and the Monarch butterfly Danaus plexippus (Nymphalidae

Nymphalidae

The Nymphalidae is a family of about 5,000 species of butterflies which are distributed throughout most of the world. These are usually medium sized to large butterflies. Most species have a reduced pair of forelegs and many hold their colourful wings flat when resting. They are also called...

), amongst others, have all been used as subjects for anatomy

Anatomy

Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant anatomy...

and physiology

Physiology

Physiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...

experiments because of their availability and large size.

Lepidopterans range in size from a few millimetres in length, such as in the case of microlepidoptera, to a wingspan of many inches, such as the Atlas moth and the world's largest butterfly Queen Alexandra's Birdwing

Queen Alexandra's Birdwing

Queen Alexandra's Birdwing is the largest butterfly in the world.The species was named by Lord Walter Rothschild in 1907, in honour of Queen Alexandra, wife of King Edward VII of the United Kingdom...

General body plan

The body of an adult butterfly or moth (imago) has three distinct divisions, called tagmata

Tagma (biology)

In invertebrate biology, a tagma is a specialized grouping of arthropod segments, such as the head, the thorax, and the abdomen with a common function. The segments of a tagma may be either fused or moveable.-Tagmata:...

, connected at constrictions; these tagmata are the head, thorax and abdomen. Adult lepidopterans have four wings: a forewing and a hindwing on both the left and the right side of the thorax and, like all insects, have three pairs of legs.

The morphological

Morphology (biology)

In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

characteristics which distinguish the order Lepidoptera from other insect orders are:

Head: The head has large compound eyes and if mouthparts are present, they are almost always a drinking straw-like proboscis.
Scales: Scales cover the external surface of the body and appendages.
Thorax: The prothorax
Prothorax
The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites are the pronotum , the prosternum , and the propleuron on each side. The prothorax never bears wings in extant insects, though some fossil groups possessed...

is usually reduced.
Wings: Two pairs of wings are present in almost all taxa. The wings have very few cross-veins
Insect wing
Insects are the only group of invertebrates known to have evolved flight. Insects possess some remarkable flight characteristics and abilities, still far superior to attempts by humans to replicate their capabilities. Even our understanding of the aerodynamics of flexible, flapping wings and how...

.
Abdomen: The posterior abdominal segments are extensively modified for reproduction. Cerci
Cercus
Cerci are paired appendages on the rear-most segments of many arthropods, including insects and arachnids but not crustaceans. Cerci often serve as sensory organs, but they may also be used as weapons or copulation aids, or they may simply be vestigial structures.Typical cerci may appear to be...

are absent.
Larva: Lepidoptera larvae are known as caterpillars, and have a well-developed head and mandibles. They can have from 0 to 5 pairs of prolegs, usually 4.
Pupa: The pupae in most species are adecticous (with no functional mandibles in the pupal state) and obtect (with appendages fused or glued to the body), while others are decticous (with functional mandibles present in the pupal state) and exarate (having the antennae, legs, and wings free).

Distinguishing taxonomic features

The chief characteristics used to classify lepidopteran species, genera and families are:

the mouthparts
the shape and venation of the wings
- whether the wings are homoneurous (the venation of the forewings and hind wings alike) or heteroneurous (forewings and hind wings different)
- whether the wings are aculeate (more or less covered with specialized bristles called microsetae) or nonaculeate
- the type of wing coupling (jugate or frenate)
the anatomy of the reproductive organs
the structure of larva and position of primary setae
whether the pupa is exarate or obtect

The morphological characteristics of caterpillars and pupae used for classification are completely different from that of adults; different classification schemes are sometimes provided separately for classifying adults, larvae and pupae. The characteristics of immature stages are increasingly used for taxonomic purposes as they provide insights into systematics and phylogenies of Lepidoptera that are not apparent from examination of adults.

Head

Like all animal heads, the head of a butterfly or moth contains the feeding organs and the major sense organs. The head typically consists of two antennae, two compound eyes, two palpi

Pedipalp

Pedipalps , are the second pair of appendages of the prosoma in the subphylum Chelicerata. They are traditionally thought to be homologous with mandibles in Crustacea and insects, although more recent studies Pedipalps (commonly shortened to palps or palpi), are the second pair of appendages of the...

and a proboscis. Lepidoptera have ocelli which may or may not be visible. They also have sensory structures called chaetosemata, the functions of which are largely unknown. The head is filled largely by the brain, the sucking pump and its associated muscle bundles. Unlike the adults, the larva

Larva

e have one-segmented mandibles.

The head capsule is well sclerotised and has a number of sclerites or plates, separated by sutures. The sclerites are difficult to distinguish from sulci (singular – sulcus) which are secondary thickenings. The regions of the head have been divided into a number of areas which act as a topographical guide for description by lepidopterists but cannot be discriminated in terms of their development. The head is covered by hair-like or lamellar scales and found either as tufts on the frons or vertex (referred to as rough-scaled) or pressed close to the head (referred to as smooth-scaled).

The sensory organs and structures on the head show great variety, and the shape and form of these structures, as also their presence or absence, are important taxonomic indicators for classifying taxa into families.

Antennae

Antennae are prominent paired appendages that project forwards between the animal's eyes and consist of a number of segments. In the case of butterflies, their length varies from half the length of the forewing to three-quarters of the length of the forewing. The antennae of butterflies are either slender and knobbed at the tip and, in the case of the Hesperiidae, are hooked at the tip. In some butterfly genera such as Libythea
Libythea
Libythea is a widespread genus of nymphalid butterflies commonly called Beaks or Snouts. They are strong fliers and may even be migratory.- Libythea classification :* Source:...

and Taractrothera the knob is hollowed underneath. Moth antennae are either filiform (thread-like), unipectinate (comb-like),bipectinate (feather-like), hooked, clubbed or thickened. Some moths have knobbed antennae akin to those of butterflies,including the families Castniidae

Castniidae

Castniidae, or castniid moths, is a small family of moths with less than 200 species: The majority are Neotropical with some in Australia and a few in south-east Asia. These are medium-sized to very large moths, usually with drab, cryptically-marked forewings and brightly coloured hindwings. They...

, Neocastniidae and Euschemonidae.

Antennae are the primary organs of olfaction (smell) in Lepidoptera. The antenna surface is covered with large numbers of olfactory scales, hairs or pits; as many as 1,370,000 are found on the antennae of a Monarch. Antennae are extremely sensitive; the feathered antennae of male moths from the Saturniidae, Lasiocampidae and many other families are so sensitive that they can detect the pheromones of female moths from distances of up to 2 km (1.2 mi) away. Lepidoptera antennae can be angled in many positions. They help the insect in locating the scent and can be considered to act as a kind of 'olfactory radar'. In moths, males frequently have antennae which are more feathery than those of the females, for detecting the female pheromones at a distance. Since females do not need to detect the males, they have simpler antennae. Antennae have also been found to play a role in the time-compensated sun compass orientation in migratory

Lepidoptera migration

Lepidoptera migration is a biological phenomenon whereby populations of butterflies or moths migrate over long distances to areas where they cannot settle for long periods of time...

Monarch butterflies.

Eyes

Lepidoptera have two large, immovable compound eyes which consist of a large number of facet

Facet

Facets are flat faces on geometric shapes. The organization of naturally occurring facets was key to early developments in crystallography, since they reflect the underlying symmetry of the crystal structure...

s or lenses, each connected to a lens-like cylinder which is attached to a nerve leading to the brain

Brain

The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

. Each eye may have up to 17,000 individual light receptors (ommatidia

Ommatidium

The compound eyes of insects, mantis shrimp and millipedes are composed of units called ommatidia . An ommatidium contains a cluster of photoreceptor cells surrounded by support cells and pigment cells. The outer part of the ommatidium is overlaid with a transparent cornea...

) which in combination provide a broad mosaic view of the surrounding area. One tropical Asian family, the Amphitheridae, has compound eyes divided into two distinct segments. The eyes are usually smooth but may be covered by minute hairs. The eyes of butterflies are usually brown, golden-brown or even red as in the case of some species of skippers

Skipper (butterfly)

A skipper or skipper butterfly is a butterfly of the family Hesperiidae. They are named after their quick, darting flight habits. There are more than 3500 recognized species of skippers and they occur worldwide, but with the greatest diversity in the Neotropical regions of Central and South...

.

While most insects have three simple eyes, or ocelli, only two ocelli are present in all species of Lepidoptera, except a few moths, one on each side of the head near the edge of the compound eye. On some species, sense organs called chaetosemata are found near the ocelli. The ocelli are not homologous

Homology (biology)

Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...

to the simple eyes of caterpillars which are differently named as stemmata. The ocelli of Lepidoptera are reduced externally in some families; where present, they are unfocussed, unlike stemmata of larvae which are fully focussed. The utility of ocelli is not understood at present.

Butterflies and moths are able to see ultra-violet

Ultraviolet

Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...

(UV) light, and wing colours and patterns are principally observed by Lepidoptera in this region. The patterns seen on their wing under UV light differ considerably from those seen in normal light. The UV patterns act as visual cues which help differentiate between species for the purpose of mating. Studies have been carried out on Lepidoptera (mostly butterflies) wing patterns illuminated by UV light.

Palpi

Typically, the labial palpi are prominent, 3-segmented, springing from under the head and curving up in front of the face. There is great variation in morphology of labial palpi in different families of Lepidoptera; sometimes the palpi are separate and sometimes they are connivent and form a beak, but they are always independently movable. In other cases, the labial palpi may not be erect but 'porrect' (projecting forward horizontally).
Palpi consist of a short basal segment, a comparatively long central segment and a narrow terminal portion. The first two segments are densely scaled and may be hirsute; the terminal segment is bare. The terminal segment may be blunt or pointed; it may project straight or at an angle from the second segment inside which it may be concealed.

Mouthparts

While mandibles or 'jaws' (chewing mouthparts) are only present in the caterpillar stage, the mouthparts of most adult Lepidoptera mainly consist of the sucking kind; this part is known as the proboscis or 'haustellum'. A few Lepidoptera species have reduced mouthparts and therefore do not feed in the adult state. Others, such as the basal

Basal (phylogenetics)

In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...

family Micropterigidae, have mouthparts of the chewing kind.

The proboscis (plural – probosces) is formed from maxillary galeae and is adapted for sucking nectar. It consists of two tubes held together by hooks and separable for cleaning. Each tube is inwardly concave, thus forming a central tube up which moisture is sucked. Suction is effected through the contraction and expansion of a sac in the head. The proboscis is coiled under the head when the insect is at rest and extended only when feeding. The maxillary palpi are reduced and even vestigial. They are conspicuous and 5-segmented in some of the more basal families and are often folded.

The shape and dimensions of the proboscis have evolved to give different species a wider and therefore more advantageous diet. There is an allometric scaling relationship between body mass of Lepidoptera and length of proboscis from which an interesting adaptive departure is the unusually long-tongued hawk moth Xanthopan morgani praedicta
Xanthopan morgani
Xanthopan morgani, or Morgan's Sphinx, is a very large hawk moth from West Africa and Madagascar. It is the sole member of its genus, and little is known of the biology, though the adults have been found to visit orchids .In January 1862 while researching insect pollination of orchids, Charles...

. Charles Darwin

Charles Darwin

Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...

predicted the existence and proboscis length of this moth before its discovery based on his knowledge of the long-spurred Madagascan star orchid Angraecum sesquipedale
Angraecum sesquipedale
Angraecum sesquipedale is an epiphytic orchid in the genus Angraecum that is endemic to Madagascar. The orchid was first discovered by the French botanist Louis-Marie Aubert du Petit-Thouars in 1798, but was not described until 1822...

.

There are primarily two feeding guilds

Guild (ecology)

A guild is any group of species that exploit the same resources, often in related ways. As can be seen from the list of examples below, it does not follow that the species within a guild occupy the same, or even similar, ecological niches...

in Lepidoptera – the nectarivorous who obtain the majority of their nutritional requirements from floral nectar and those of the frugivorous guild who feed primarily on juices of rotting fruit or fermenting tree sap. There are substantial differences between the morphology of the probosces of both feeding guilds. Hawkmoths (family Sphingidae

Sphingidae

Sphingidae is a family of moths , commonly known as hawk moths, sphinx moths and hornworms, that includes about 1,200 species . It is best represented in the tropics but there are species in every region . They are moderate to large in size and are distinguished among moths for their rapid,...

) have elongated probosces which enable them to feed on and pollinate flowers with long tubular corrollas. Besides this, a number of taxa (especially noctuid

Noctuidae

The Noctuidae or owlet moths are a family of robustly-built moths that includes more than 35,000 known species out of possibly 100,000 total, in more than 4,200 genera. They constitute the largest family in the Lepidoptera....

moths) have evolved different proboscis morphologies. Certain noctuid species have developed piercing mouthparts; the proboscis has sclerotised scales on the tip which to pierce and suck blood or fruit juices. Probosces in some Heliconius
Heliconius
Heliconius comprise a colorful and widespread brush-footed butterfly genus distributed throughout the tropical and subtropical regions of the New World. These butterflies utilize Passion flower plants as their larval food source and rely on bright wing color patterns to signal their distastefulness...

species have evolved to consume solids such as pollen

Pollen

Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...

. Some other moths, mostly noctuids, have modified probosces to suit their mode of nutrition – lachryphagy (feeding on tears).

Thorax

The thorax, which develops from segments 2, 3 and 4 of the larva, consists of three invisibly divided segments, namely prothorax

Prothorax

The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites are the pronotum , the prosternum , and the propleuron on each side. The prothorax never bears wings in extant insects, though some fossil groups possessed...

, metathorax

Metathorax

The metathorax is the posterior of the three segments in the thorax of an insect, and bears the third pair of legs. Its principal sclerites are the metanotum , the metasternum , and the metapleuron on each side...

and mesothorax

Mesothorax

The mesothorax is the middle of the three segments in the thorax of an insect, and bears the second pair of legs. Its principal sclerites are the mesonotum , the mesosternum , and the mesopleuron on each side...

. The organs of insect locomotion – the legs and wings – are borne on the thorax. The forelegs spring from the prothorax, the forewings and middle pair of legs are borne on the metathorax, and the hindwings and hindlegs arise from the mesothorax. In some cases, the wings are vestigial.

The upper and lower parts of the thorax (sterna and terga

Tergum

A tergum is the dorsal portion of an arthropod segment other than the head. The anterior edge is called the base and posterior edge is called the apex or margin. A given tergum may be divided into hardened plates or sclerites commonly referred to as tergites...

respectively) are composed of segmental and intrasegmental sclerite

Sclerite

s which display secondary sclerotisation and considerable modification in the Lepidoptera. The prothorax is the simplest and smallest of the three segments while the mesothorax is the most developed.

Between the head and thorax is the membranous neck or cervix. It comprises a pair of lateral cervical sclerites and is composed of both cephalic and thoracic elements. Between the head and the thorax is a tufted scale called the pronotum. On either side is a shield-like scale called a scapula. In the Noctuoidea

Noctuoidea

Noctuoidea is the superfamily of noctuid or "owlet" moths, and has the largest number of species described for any Lepidopteran superfamily. Its classification has not yet reached a satisfactory or stable state. The most recent classifications include only four families in the superfamily;...

, the metathorax is modified with a pair of tympanal organ

Tympanal organ

A tympanal organ is a hearing organ in insects, consisting of a membrane stretched across a frame backed by an air sac and associated sensory neurons...

Leg

Fore-legs in the Papilionoidea

Papilionoidea

The superfamily Papilionoidea contains all the butterflies except for the skippers, which are classified in superfamily Hesperioidea, and the moth-like Hedyloidea....

exhibit reduction of various forms: the butterfly family Nymphalidae

Nymphalidae

, or brush-footed butterflies as they are commonly known, have only the rear two pairs of legs fully functional with the forward pair strongly reduced and not capable of walking or perching. In the Lycaenidae, the tarsus is unsegmented, as the tarsomeres are fused, and, tarsal claws are absent. The aroliar pad ( a pad projecting between the tarsal claws of some insects) and pulvilli (singular : pulvillus, a pad or lobe beneath each tarsal claw) are reduced or absent in the Papilionidae. The tarsal claws are also absent in the Riodinidae

Riodinidae

The Riodinidae are a family of butterflies. The common name "metalmarks" refers to the small metallic-looking spots commonly found on their wings. There are approximately 1,000 species of metalmark butterflies in the world...

.

In Lepidoptera, the three pairs of legs are covered with scales. Lepidoptera also have olfactory organs on their feet which aid in "tasting" or "smelling" food plants.

Wings

See glossary
Glossary of Lepidopteran terms
This glossary describes the terms used in the formal descriptions of insect species, jargon used mostly by professionals or entomologist....

for terms used

Adult Lepidoptera have two pairs of membranous wings covered, usually completely, by minute scales. A wing consists of an upper and lower membrane which are connected by minute fibres and strengthened by a system of thickened hollow ribs, popularly but incorrectly referred to as 'veins', as they may also contain tracheae, nerve fibres and blood vessels. The membranes are covered with minute scales which have jagged ends or hairs and are attached by hooks. The wings are moved by the rapid muscular contraction and expansion of the thorax.

The wings arise from the meso- and meta-thoracic segments and are similar in size in the basal groups. In more derived groups, the meso-thoracic wings are larger with more powerful musculature at their bases and more rigid vein structures on the costal edge.

Besides providing the primary function of flight, wings also have secondary functions of self-defence

Self-defense

Self-defense, self-defence or private defense is a countermeasure that involves defending oneself, one's property or the well-being of another from physical harm. The use of the right of self-defense as a legal justification for the use of force in times of danger is available in many...

, camouflage and thermoregulation. In some Lepidoptera families such as the Psychidae and Lymantriidae

Lymantriidae

Lymantriidae is a family of moths. Many of its component species are referred to as "Tussock moths" of one sort or another. The caterpillar, or larval, stage of these species often has a distinctive appearance of alternating bristles and haired projections...

, the wings are reduced or even absent (often in the female but not the male).

Shape

The shape of wings exhibits great variety in Lepidoptera. In the case of the Papilionoidea, the costa may be straight or highly arched. It is sometimes concave on the hindwing. It is occasionally serrate or minutely saw-toothed on the forewing. The apex may be rounded, pointed or falcate (produced, and concave below). The termen

Termen

Termen is a municipality in the district of Brig in the canton of Valais in Switzerland.-Geography:Termen has an area, , of . Of this area, 42.2% is used for agricultural purposes, while 27.2% is forested. Of the rest of the land, 3.3% is settled and 27.4% is unproductive land.The municipality...

tends to be straight or concave on the forewing while it is usually more or less convex on the hindwing. The termen is often crenulate or dentate, i.e. produced at each vein and concave in between them. The dorsum is normally straight but may be concave.

The hindwing is frequently caudate

Tail

The tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, reptiles, and birds...

, i.e. the veins near the end of the tornus have one or more tails. The tornus itself being often produced and frequently lobed. Along the hindwing termen there are tightly-packed scales in a double row. The underside of the scales project and form a regular narrow fringe referred to as cilia.

Venation

Tubular veins run through the two-layered membranous wing. Veins are connected to the haemocoel and in theory allow haemolymph to flow through them. In addition, a nerve and trachea may pass through the veins.

Lepidopteran venation is simple in that there are few crossbars. The wing venation in Lepidoptera is a diagnostic for distinguishing between the taxa as also the genera and families. The terminology is based on the Comstock-Needham system which gives the morphological description of insect wing

Insect wing

venation. In the basal Lepidoptera, the venation of the forewing is similar to that of the hindwing; a condition referred to as "homoneurous". The Micropterigidae

Micropterigidae

(Zeugloptera) have venation that resembles the most primitive caddisflies (Trichoptera). All other Lepidoptera, the vast majority (around 98%), are "heteroneurous", the venation of the hindwing differing from that from the forewing and being sometimes reduced. Moths of the families Nepticulidae

Nepticulidae

Nepticulidae is a family of very small moths with a worldwide distribution. They are characterised by eyecaps over the eyes . These pigmy moths or midget moths, as they are commonly known, include the smallest of all living moths, with a wingspan that can be as little as 3 mm...

, Opostegidae

Opostegidae

Opostegidae or "white eyecap moths" is a family of insects in the Lepidoptera order that is characterised by particularly large eyecaps over the compound eyes...

, Gracillariidae

Gracillariidae

Gracillariidae is an important family of insects in the order Lepidoptera and the principal family of leaf miners that includes several economic, horticultural or recently invasive pest species such as the horse-chestnut leaf miner, Cameraria ohridella....

, Tischeriidae and Bucculatricidae

Bucculatricidae

Bucculatricidae or is a family of moths. This small family has representatives in all parts of the world. Some authors place the group as a subfamily of the family Lyonetiidae....

, amongst others, often have greatly reduced venation in both wings. Homoneurous moths tend to have the "jugum" form of wing-coupling as opposed to the "frenulum–retinaculum" arrangement in the case of more advanced families.

Wing coupling

The Lepidoptera have developed a wide variety of morphological wing-coupling mechanisms in the imago which render these taxa "functionally dipterous". All but the most basal forms exhibit this wing coupling. There are three different types of mechanisms – jugal, frenulo–retinacular and amplexiform.

The more primitive groups have an enlarged lobe-like area near the basal posterior margin (i.e. at the base of the forewing) called a jugum, that folds under the hindwing during flight. Other groups have a frenulum

Frenulum

A frenulum is a small fold of tissue that secures or restricts the motion of a mobile organ in the body.-In human anatomy:...

on the hindwing that hooks under a retinaculum

Retinaculum (moth)

Some four-winged insect orders, such as the Lepidoptera, have developed a wide variety of morphological wing-coupling mechanisms in the imago which render these taxa as "functionally dipterous"...

on the forewing.

In all butterflies (with the exception of male Euschemoninae) and in Bombycoidea

Bombycoidea

Bombycoidea is a superfamily of moths. It contains the silk moths, emperor moths, sphinx moths and relatives. The Lasiocampoidea are close relatives and sometimes merged in the present group. Their larvae exhibit horns.-Sources:...

moths (with the exception of the Sphingidae

Sphingidae

), there is no arrangement of frenulum and retinaculum to couple the wings. Instead, an enlarged humeral area of the hindwing is broadly overlapped by the forewing. Despite the absence of a specific mechanical connection, the wings overlap and operate in phase. The power stroke of the forewing pushes down the hindwing in unison. This type of coupling is a variation of frenate type but where the frenulum and retinaculum are completely lost.

Scales

The wings of Lepidoptera are minutely scaled, which gives the name to this order; the name 'Lepidoptera' was coined in 1735 by Carl Linnaeus for the group of "insects with four scaly wings". It is derived from Ancient Greek

Ancient Greek

lepidos or λεπίδος (scale), itself originating from the Greek lepis (female genitive singular form lepidos) meaning "(fish) scale" (and related to lepein "to peel") and pteron or πτερόν (wing).

Scales also cover the head, parts of the thorax and abdomen as well as parts of the genitalia. The morphology of scales has been studied by Downey & Allyn (1975) and scales have been classified into three groups, namely hair-like, or piliform, blade-like, or lamellar and other variable forms.

Primitive moths (non-Glossata and Eriocranidae) have 'solid' scales which are imperforate, i.e., they lack a lumen

Lumen (anatomy)

A lumen in biology is the inside space of a tubular structure, such as an artery or intestine...

.

A few taxa of the Trichoptera

Trichoptera

The caddisflies are an order, Trichoptera, of insects with approximately 12,000 described species. Also called sedge-flies or rail-flies, they are small moth-like insects having two pairs of hairy membranous wings...

(caddisflies), which are the sister group to the Lepidoptera, have hair-like scales, but always on the wings and never on the body or other parts of the insect. Caddisflies also possess caudal cerci on the abdomen, a feature absent in the Lepidoptera. According to Scoble (2005), "morphologically, scales are macrotrichia, and thus homologous with the large hairs (and scales) that cover the wings of Trichoptera (caddisflies)".

Structure

Although there is great diversity in scale form, they all share a similar structure. Scales, like other macrochaetes, arise from special trichogenic (hair-producing) cells and have a socket which is enclosed in a special 'tormogen' cell; this arrangement provides a stalk or pedicel by which scales are attached to the substrate. Scales may be piliform (hairlike) or flattened. The body or 'blade' of a typical flattened scale consists of an upper and lower lamella with an air-space in between. The surface towards the body is smooth and known as the inferior lamella. The upper surface, or superior lamella, has transverse and longitudinal ridges and ribs. The lamellae are held apart by struts called trabaculae and contain pigments which give colour. The scales cling somewhat loosely to the wing and come off easily without harming the butterfly.

Colour

The scales on butterfly wings are pigmented with melanin

Melanin

Melanin is a pigment that is ubiquitous in nature, being found in most organisms . In animals melanin pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acids, and their reduced forms...

s that can produce the colours black and brown. The white colour in the butterfly family Pieridae

Pieridae

The Pieridae are a large family of butterflies with about 76 genera containing approximately 1,100 species, mostly from tropical Africa and Asia. Most pierid butterflies are white, yellow or orange in coloration, often with black spots...

is a derivative of uric acid

Uric acid

Uric acid is a heterocyclic compound of carbon, nitrogen, oxygen, and hydrogen with the formula C5H4N4O3. It forms ions and salts known as urates and acid urates such as ammonium acid urate. Uric acid is created when the body breaks down purine nucleotides. High blood concentrations of uric acid...

, an excretory product. Bright blues, greens, reds and iridescence

Iridescence

Iridescence is generally known as the property of certain surfaces which appear to change color as the angle of view or the angle of illumination changes...

are usually created not by pigments but through the microstructure of the scales. This structural coloration is the result of coherent scattering of light by the photonic crystal

Photonic crystal

Photonic crystals are periodic optical nanostructures that are designed to affect the motion of photons in a similar way that periodicity of a semiconductor crystal affects the motion of electrons...

nature of the scales. The specialised scales that provide structural colours to reflected light mostly produce ultra-violet patterns which are discernible in that part of the ultra-violet spectrum that Lepidopteran eyes can see. The structural colour seen is dependent upon the angle of view. For example, in Morpho cypris
Morpho cypris
The Cypris Morpho is a Neotropical butterfly.It is found in Panama , Costa Rica , Nicaragua, Colombia and Ecuador.Several subspecies and many forms have been described.-References:...

, the colour from the front is a bright blue but when seen from an angle changes very quickly to black.

The iridescent structural colouration on the wings of many lycaenid and papilionid species, such as Parides sesostris
Parides sesostris
Parides sesostris is a species of butterfly in the family Papilionidae native to the Americas. It is commonly known as the Emerald-patched Cattleheart and the Southern Cattleheart. The larvae feed on Aristolochia barbata, A. bicolor, A. grandiflora, A. sprucei, and A. trianae...

and Teinopalpus imperialis
Teinopalpus imperialis
The Kaiser-i-Hind is a rare species of swallowtail butterfly found from Nepal and north India east to north Vietnam. The common name literally means "Emperor of India". The Kaiser-i-hind is much sought after by butterfly collectors for its beauty and rarity...

, and lycaenids such as Callophrys rubi, Cyanophrys remus, and Mitoura gryneus, has been studied. They manifest the most complex photonic scale architectures known – regular three-dimensional periodic lattices, that occur within the lumen of some scales. In the case of the Kaiser-i-Hind (Teinopalpus imperialis
Teinopalpus imperialis
The Kaiser-i-Hind is a rare species of swallowtail butterfly found from Nepal and north India east to north Vietnam. The common name literally means "Emperor of India". The Kaiser-i-hind is much sought after by butterfly collectors for its beauty and rarity...

), the three-dimensional photonic structure has been examined by transmission electron tomography and computer modelling to reveal naturally occurring "chiral tetrahedral repeating units packed in a triclinic lattice", the cause of the iridescence.

Function

Scales play an important part in the natural history of Lepidoptera. Scales enable the development of vivid or indistinct patterns which help the organism protect itself by camouflage

Camouflage

, mimicry and warning. Besides providing insulation

Thermal insulation

, dark patterns on wings allow sunlight to be absorbed and are probably involved in thermoregulation. Bright and distinctive colour patterns in butterflies which are distasteful to predators help communicate

Aposematism

Aposematism , perhaps most commonly known in the context of warning colouration, describes a family of antipredator adaptations where a warning signal is associated with the unprofitability of a prey item to potential predators...

their toxicity or inedibility, thus preventing predatation. In Batesian mimicry

Batesian mimicry

Batesian mimicry is a form of mimicry typified by a situation where a harmless species has evolved to imitate the warning signals of a harmful species directed at a common predator...

, wing colour patterns help edible Lepidopterans mimic inedible models, while in Müllerian mimicry

Müllerian mimicry

Müllerian mimicry is a natural phenomenon when two or more harmful species, that may or may not be closely related and share one or more common predators, have come to mimic each other's warning signals...

, inedible butterflies resemble each other to reduce the numbers of individuals sampled by predators.

Scales may have evolved initially for providing insulation. Scales on the thorax and other parts of the body may contribute to maintaining the high body temperatures required during flight. The 'solid' scales of basal moths are however not as efficient as those of their more advanced relatives as the presence of a lumen adds air layers and increases the insulation value. Scales also help increase the lift to drag ratio in gliding flight.

For newly emerged adults of most myrmecophilous

Myrmecophily

Myrmecophily is the term applied to positive interspecies associations between ants and a variety of other organisms such as plants, arthropods, and fungi...

Lycaenidae

The Lycaenidae are the second-largest family of butterflies, with about 6000 species worldwide, whose members are also called gossamer-winged butterflies...

, deciduous waxy scales provide some protection from predators as they emerge from the nest. In the case of the Moth butterfly (Liphyra brassolis
Liphyra brassolis
The Moth Butterfly is a butterfly found in Asia and Australia that belongs to the lycaenid family. The larvae are predatory and feed on ant larvae. This is one of the largest species of Lycaenid butterfly. Several disjunct populations across its wide distribution range are considered as sub-species...

), the caterpillars are unwelcome guests in nests of tree ants, feeding on ant larvae. The adults emerging from pupae are covered with soft, loose adhesive scales which rub off and stick on the ants as they make their way out of the nest after hatching.

Androconia

Male Lepidoptera possess special scales, called androconia (singular – androconium), which have evolved as a result of sexual selection

Sexual selection

Sexual selection, a concept introduced by Charles Darwin in his 1859 book On the Origin of Species, is a significant element of his theory of natural selection...

for the purposes of disseminating pheromone

Pheromone

s for attracting suitable mates. Androconia may be dispersed on the wings, body, or legs or occur in patches, referred to as "brands" or "stigmata" on the wings, usually in invaginations of the upper surface of the forewings, sometimes concealed by other scales. Androconia are also known to occur in the folds of wings. These brands sometimes consist of hairlike tufts which facilitate the diffusion of the pheromone. The role of androconia in the courtship of pierid and nymphalid butterflies has been proven experimentally.

Successive close-ups of the scales of a Peacock wing

Abdomen

The abdomen

Abdomen

In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...

or body is composed of nine segments. In the larva it ranges from segments 5 to 13. The eleventh segment of the larva holds a pair of anal claspers, which protude in some taxa

Taxon

|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...

and represent the genitalia.

Many families of moths have special organs to help detect bat echolocation

Animal echolocation

Echolocation, also called biosonar, is the biological sonar used by several kinds of animals.Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects...

. These organs are known as tympana
Tympanal organ
A tympanal organ is a hearing organ in insects, consisting of a membrane stretched across a frame backed by an air sac and associated sensory neurons...

(singular – typanum). The Pyraloidea

Pyraloidea

The Pyraloidea are a moth superfamily containing about 16,000 described species worldwide , and probably at least as many more remain to be described. They are generally fairly small moths....

and almost all Geometroidea

Geometroidea

Geometroidea is the superfamily of geometrid moths in the Lepidoptera. It includes the families Geometridae, Uraniidae, and Sematuridae...

have tympana located on the anterior sternite of the abdomen. The Noctuoidea

Noctuoidea

also have tympana, but in their case, the tympana are located on the underside of the metathorax

Metathorax

, the structure and position of which are unique and a taxonomic distinguishing feature of the superfamily.

The females of some moths have a scent-emitting organ located at the tip of the abdomen.

Genitalia

The genitalia are complex and provide the basis for species discrimination in most families and also in family identification. The genitalia arise from the tenth or most distal segment of the abdomen. Lepidoptera have some of the most complex genital structures of all insects, with a wide variety of complex spines, setae, scales and tufts in males, claspers of different shapes and different modifications of the ductus bursae in females, through which stored sperm is transferred within the female directly, or indirectly, to the vagina for fertilisation.

The arrangement of genitalia is important in courtship and mating as they prevent cross-specific mating and hybridisation. The uniqueness of a species' genitalia led to the use of the morphological study of genitalia as one of the most important keys in taxonomic identification of taxa below family level. With the advent of DNA analysis, the study of genitalia has now become just one of the techniques used in taxonomy.

There are three basic configurations of genitalia in the majority of the Lepidoptera based on how the arrangement in females of openings for copulation, fertilisation and egg-laying has evolved:

Exoporia
Exoporia
Exoporia are a group of primitive Lepidoptera comprising the superfamilies Mnesarchaeoidea and Hepialoidea . Exoporia is a natural group or clade which is the sister group of the lepidopteran infraorder Heteroneura...

n : Hepialidae
Hepialidae
The Hepialidae is a family of insects in the lepidopteran order. Moths of this family are often referred to as swift moths or ghost moths.-Taxonomy and systematics:...

and related families have an external groove that carries sperm from the copulatory opening (gonopore) to the (ovipore) and are termed Exoporian.
Monotrysia
Monotrysia
The Monotrysia is a group of insects in the Lepidopteran order which is not currently considered to be a natural group or clade. The group contains only moths and most of these are small and are relatively understudied in many regions of the world...

n : Primitive groups have a single genital aperture near the end of the abdomen through which both copulation and egg laying occur. This character is used to designate the Monotrysia.
Ditrysia
Ditrysia
The Ditrysia are a natural group or clade of insects in the Lepidopteran order containing both butterflies and moths. They are so named because the female has two distinct sexual openings: one for mating, and the other for laying eggs .About 98% of described species of Lepidoptera belong to Ditrysia...

n : The remaining groups have an internal duct that carry sperm and form the Ditrysia, with separate openings for copulation and egg-laying.

The genitalia of the male and female in any particular species are adapted to fit each other like a lock (male) and key (female). In males, the ninth abdominal segment is divided into a dorsal

Dorsum (biology)

In anatomy, the dorsum is the upper side of animals that typically run, fly, or swim in a horizontal position, and the back side of animals that walk upright. In vertebrates the dorsum contains the backbone. The term dorsal refers to anatomical structures that are either situated toward or grow...

'tegumen' and ventral 'viniculum'. They form a ring-like structure for the attachment of genital parts and a pair of lateral clasping organs (claspers or 'harpe'). The male has a median tubular organ (called the aedeagus

Aedeagus

An aedeagus is a reproductive organ of male insects through which they secrete sperm from the testes during copulation with a female insect...

) which is extended through an eversible sheath (or 'vesica') to inseminate the female. The males have paired sperm ducts in all lepidopterans; the paired testes are separate in basal taxa and fused in advanced forms.

While the layout of internal genital ducts and openings of the female genitalia depends upon the taxonomic group that insect belongs to, the internal female reproductive system of all lepidopterans consists of paired ovaries and accessory glands which produce the yolks and shells of the eggs. Female insects have a system of receptacles and ducts in which sperm is received, transported and stored. The oviducts of the female join together to form a common duct (called the 'oviductus communis') which leads to the vagina.

When copulation takes place, the male butterfly or moth places a capsule of sperm (spermatophore

Spermatophore

A spermatophore or sperm ampulla is a capsule or mass created by males of various animal species, containing spermatozoa and transferred in entirety to the female's ovipore during copulation...

) in a receptacle of the female (called the corpus bursae). The sperm, when released from the capsule, swims directly into or via a small tube into a special seminal receptacle (spermatheca

Spermatheca

The spermatheca , also called receptaculum seminis , is an organ of the female reproductive tract in insects, some molluscs, oligochaeta worms and certain other invertebrates and vertebrates...

), where the sperm is stored until it is released into the vagina for fertilisation during egg laying, which may occur hours, days, or months after mating. The eggs pass through the ovipore

Ovipore

An ovipore is a pore-like sexual organ of a female insect that gets inseminated by the spermatophores ejected by the aedeagus of a male insect during copulation. The spermatophores that pass through the ovipore are stored in most insect species in another organ called spermatheca....

. The ovipore may be at the end of a modified ovipositor or surrounded by a pair of broad setose anal papillae.

Butterflies of the Parnassinae (Family Papilionidae) and some Acraeini

Acraeini

Acraeini is a tribe of butterflies of the subfamily Heliconiinae in the family Nymphalidae.-Genera:* Abananote Potts, 1943* Acraea – acraeas* Actinote* Altinote Potts, 1943* Bematistes* Cethosia – lacewings...

(Family Nymphalidae) add a post-copulatory plug, called the sphragis, to the abdomen of the female after copulation preventing her from mating again.

The males of many species of Papilionoidea are furnished with secondary sexual characteristics. These consist of scent-producing organs, brushes, and brands or pouches of specialised scales. These presumably meet the function of convincing the female that she is mating with a male of the correct species.

Development

The fertilised egg matures and hatches to give a caterpillar. The caterpillar is the feeding stage of the Lepidopteran life-cycle. The caterpillar needs to be able to feed and to avoid being eaten and much of its morphology has evolved to facilitate these two functions. After growth and ecdysis

Ecdysis

, the caterpillar enters into a sessile developmental stage called a pupa (or chrysalis) around which it may form a casing. The insect develops into the adult in the pupa stage; when ready the pupa hatches and the adult stage or imago of a butterfly or moth arises.

Egg

Like most insects, the Lepidoptera are oviparous or 'egg-layers'. Lepidopteran eggs, like those of other insects, are centrolecithal

Centrolecithal

Centrolecithal is the placement of the yolk in the centre of the cytoplasm of ovums. Many arthropod eggs are centrolecithal....

in that the eggs have a central yolk surrounded by cytoplasm

Cytoplasm

The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...

. The yolk provides the liquid nourishment for the embryo

Embryo

An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

caterpillar until it escapes from the shell. The cytoplasm is enclosed by the vitteline envelope

Vitteline envelope

The vitteline envelope is the outer proteinaceous layer outside the oocyte in an insect egg. The vitteline envelope, not being a cellular structure, is not referred to as a membrane. It varies in thickness for different insects and even varies at different parts of the egg...

and a proteinaceous membrane called the chorion

Chorion (egg)

The chorion is the outermost membrane around the embryo in mammals, birds and reptiles. It develops from an outer fold on the surface of the yolk sac. In insects, the chorion is the outer shell of the insect egg, which lies outside the vitteline envelope and is developed by the follicle cells while...

protects the egg externally. The zygote nucleus is located posteriorly.

In some species of Lepidoptera, a waxy layer is present inside the chorion adjacent to the vitelline layer which is thought to have evolved to prevent desiccation. In insects, the chorion has a layer of air-pores in the otherwise solid material which provides very limited capability for respiratory function. In Lepidoptera, the chorion layer above this air pore layer is lamellar with successive sheets of protein arranged in a particular direction and stepped so as to form a helical arrangement.

The top of the egg is depressed and forms a small central cavity called micropyle

Micropyle

A micropyle is small opening in the surface of an ovule, through which the pollen tube penetrates, often visible as a small pore in the ripe seed....

through which the egg is fertilised. The micropyle is situated on top in eggs which are globular, conical, or cylindrical; in those eggs which are flattened or lenticular, the micropyle is located on the outer margin or rim.

The eggs of Lepidoptera are usually rounded and small (1 mm) though they may be as large as 4 mm in the case of Sphingidae

Sphingidae

and Saturniidae

Saturniidae

. They are generally quite plain in colour, white, pale green, bluish-green, or brown. Butterfly and moth eggs come in various shapes; some are spherical, others hemispherical, conical, cylindrical or lenticular (lens-shaped). Some are barrel-shaped or pancake-shaped, while others are turban or cheese-shaped. They may be angled or depressed at both ends, ridged or ornamented, spotted or blemished.

The eggs are deposited singly, in small clusters, or in a mass, and invariably on or near the food source. Captive moths have been known to lay eggs in the cages they have been sequestered in. Egg size in the Lepidoptera is affected by a number of factors. Lepidoptera species which overwinter

Hibernation

Hibernation is a state of inactivity and metabolic depression in animals, characterized by lower body temperature, slower breathing, and lower metabolic rate. Hibernating animals conserve food, especially during winter when food supplies are limited, tapping energy reserves, body fat, at a slow rate...

in the egg stage usually have larger eggs than the species that do not. Similarly, species feeding on woody plants in larval stage have larger eggs than those species feeding on herbaceous plants. Eggs laid by older females of a few butterfly species have been noted to be smaller in size than their younger counterparts. In the absence of adequate nutrition, the females of the corn-borer moth ( Ostrinia
Ostrinia
Ostrinia is a genus of moths in the Crambidae family. Several of them, including the European Corn Borer, are agricultural pests.-Species:*Ostrinia avarialis Amsel, 1970*Ostrinia dorsivittata...

spp.) have been recorded to lay clutches with egg sizes below normal.

While escaping, the newly hatched larvae of many species sometimes eat the chorion to emerge. Alternatively, the egg shell may have a line of weakness around the cap which gives way allowing the larva to emerge. The egg shell and a small amount of yolk trapped in the amniotic membranes forms the first food for most lepidopteran larvae.

Caterpillar

Caterpillars, are "characteristic polypod larvae with cylindrical bodies, short thoracic legs and abdominal prolegs (pseudopods)". They have a toughened (sclerotised

Sclerite

) head capsule, mandibles (mouthparts) for chewing, and a soft tubular, segmented body, that may have hair-like or other projections, 3 pairs of true legs, and additional proleg

Proleg

s (up to 5 pairs). The body consists of 13 segments, of which 3 are thoracic (T1, T2 and T3) and 10 are abdominal (A1 to A10).

All true caterpillars have an upside-down Y-shaped line that runs from the top of the head downward. In between the Y-shaped line lies the frontal triangle or frons. The clypeus

Clypeus

The clypeus is one of the sclerites that makes up the "face" of an arthropod.In insects, the clypeus delimits the lower margin of the face, with the labrum articulated along the ventral margin of the clypeus. The mandibles bracket the labrum, but do not touch the clypeus. The dorsal margin of the...

, located below the frons, lies between the two antennae

Antenna (biology)

. The labrum is found below the clypeus. There is a small notch in the centre of the labrum with which the leaf edge engages when the caterpillar eats.

The larvae have silk glands which are located on the labium. These glands are modified salivary gland

Salivary gland

The salivary glands in mammals are exocrine glands, glands with ducts, that produce saliva. They also secrete amylase, an enzyme that breaks down starch into maltose...

s. They use these silk glands to make silk for cocoons and shelters. Located below the labrum are the mandibles. On each side of the head there are usually six stemmata just above the mandibles. These stemmata are arranged in a semicircle. Below the stemmata there is a small pair of antennae, one on each side.

The thorax bears three pairs of legs, one pair on each segment. The prothorax (T1) has a functional spiracle which is actually derived from the mesothorax (T2) while the metathorax has a reduced spiracle which is not externally open and lies beneath the cuticle. The thoracic legs consist of coxa, trochanter, femur, tarsus and claw and are constant in form throughout the order. However they are reduced in the case of certain leaf-miners and elongated in certain Notodontidae

Notodontidae

Notodontidae is a family of moths with approximately 3,500 known species. Moths of this family are found in all parts of the world, but they are most concentrated in tropical areas, especially in the New World...

. In Micropterigidae, the legs are three-segmented, as the coxa, trochanter and femur are fused.

Abdominal segments 3–6 and 10 each bear a pair of legs that are more fleshy. The thoracic legs are known as true legs and the abdominal legs are called prolegs. The true legs vary little in the Lepidoptera except for reduction in certain leaf-miners and elongation in the family Notodontidae

Notodontidae

. The prolegs contain a number of small hooks on the tip, which are known as crochets. The families of Lepidoptera differ in the number and positioning of their prolegs. Some larvae such as inchworms (Geometridae) and loopers (Plusiinae

Plusiinae

Plusiinae is a smallish subfamily of the moth family Noctuidae. As the Noctuidae appear to be a paraphyletic assemblage, the Plusiinae may eventually be raised to family status ....

) have five pairs of prolegs or less, while others like Lycaenidae

Lycaenidae

The Lycaenidae are the second-largest family of butterflies, with about 6000 species worldwide, whose members are also called gossamer-winged butterflies...

and slug caterpillars (Limacodidae

Limacodidae

Limacodidae or Euclidae is a family of moths in the superfamily Zygaenoidea or the Cossoidea; the placement is in dispute. They are often called slug moths because their caterpillars bear a distinct resemblance to slugs...

) lack prolegs altogether. In some leaf-mining caterpillars there are crochets present on the abdominal wall which are reduced prolegs, while other leaf-mining species lack the crochets entirely. The abdominal spiracles are located on each side of the body on the first eight abdominal segments.

Caterpillars have different types of projections; setae (hairs), spines, warts, tubercles, and horns. The hairs come in an assortment of colours and may be long or short; single, in clusters, or in tufts; thinner at the point or clubbed at the end. A spine may either be a chalaza (having a single point) or a scolus (having multiple points). The warts may either be small bumps or short projections on the body. The tubercles are fleshy body projections that are either short and bump-like or long and filament-like. They usually occur in pairs or in a cluster on one or more segments. The horns are short, fleshy, and are drawn to a point. They are usually found on the eighth abdominal segment.

A large number of species of families Saturniidae

Saturniidae

, Limacodidae

Limacodidae

and Megalopygidae

Megalopygidae

Megalopygidae is the technical name of a group of insect species known generally as crinkled flannel moths, or simply Flannel Moths. They occur in North America and the New World tropics. The larvae are called Puss Caterpillars, and with their long hairs, resemble cotton balls...

have stinging caterpillars which have poisonous setae, also called urticating hair

Urticating hair

Urticating hairs, i.e. stinging hairs, are one of the primary defense mechanisms used by numerous plants, some New World tarantulas, and various lepidopteran caterpillars. Urtica is Latin for "nettle", and hairs that urticate are characteristic of this type of plant, and many other plants in...

s, and in the case of Lonomia
Lonomia
The genus Lonomia is a moderate-sized group of fairly cryptic saturniid moths from South America, famous not for the adults, but for their highly venomous caterpillars, which are responsible for a few deaths each year , especially in southern Brazil, and the subject of hundreds of published medical...

– a Brazil

Brazil

Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

ian saturniid genus – can kill a human due to its potent anticoagulant

Anticoagulant

An anticoagulant is a substance that prevents coagulation of blood. A group of pharmaceuticals called anticoagulants can be used in vivo as a medication for thrombotic disorders. Some anticoagulants are used in medical equipment, such as test tubes, blood transfusion bags, and renal dialysis...

poison. Caterpillars of many taxa that have sequestered toxic chemicals from host-plants or have sharp urticating hair or spines, display aposematic

Aposematism

colouration and markings.

Caterpillars undergo ecdysis

Ecdysis

and have a number of larval instar

Instar

s, usually five but varying between species. The new cuticle is soft and allows the increase in size and development of the caterpillar before becoming hard and inelastic. In the last ecdysis, the old cuticle splits and curls up into a small ball at the posterior end of the pupa and is known as the larval exuvia

Exuvia

Exuviae is a term used in biology to describe the remains of an exoskeleton and related structures that are left after ecdysozoans have moulted...

Chrysalis or pupa

A cocoon is a casing spun of silk

Silk

Silk is a natural protein fiber, some forms of which can be woven into textiles. The best-known type of silk is obtained from the cocoons of the larvae of the mulberry silkworm Bombyx mori reared in captivity...

by many moth caterpillars, and numerous other holometabolous insect larva

Larva

e as a protective covering for the pupa. Most Lepidoptera larvae will either make a cocoon

Pupa

and pupate

Metamorphosis

inside them or will pupate in a cell under the ground, with the exception of butterflies and advanced moths such as noctuids

Noctuidae

, whose pupae are exposed. The pupae of moths are usually brown and smooth whereas butterfly pupae are often colourful and their shape varies greatly. In butterflies, the exposed pupa is often referred to as a chrysalis, derived from the Greek

Greek language

Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

term "chrysalis": () for gold

Gold

Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

, referring to the golden colour of some pupae.

The caterpillars of many butterflies attach themselves by a button of silk to the underside of a branch or stone or other projecting surface. They remain attached to the silk pad by a hook-like process called a cremaster. Most chrysalids hang head downward, but in the families Papilionidae, Pieridae, and Lycaenidae, the chrysalis is held in a more upright position by a silk girdle around the middle of the chrysalis.

The pupae of most Lepidoptera are obtect, with appendages fused or glued to the body, while the rest have exarate pupae, having the antennae, legs, and wings free and not glued to the body.

During the pupal stage, the morphology of the adult is developed through elaboration from larval structures. The general aspect of the adult is visible before the outer surface hardens – the head, resting on the thorax, the eyes, antennae (brought forward over the head), the wings brought over the thorax and the six legs between the wings and the abdomen. Among the features discernible in the head region of a pupa are sclerites, sutures, pilifers, mandibles, eye-pieces, antennae, palpi and the maxillae. The pupal thorax displays the three thoracic segments, legs, wings, tegulae, alar furrows and axillary tubercles. The pupal abdomen exhibits the ten segments, spines, setae, scars of larval prolegs and tubercles, anal and genital openings, as well as spiracles. The pupa of borers display the flange-plates while those of specialised Lepidoptera exhibit the cremaster.

While the pupa is generally stationary and immobile, those of the primitive moth families Micropterigidae

Micropterigidae

, Agathiphagidae and Heterobathmiidae have fully functional mandibles. These serve principally to allow the adult to escape from the cocoon. Besides this, all appendages and the body are separate from the pupal skin and enjoy a degree of independent motion. All other superfamilies of the Lepidoptera are more specialised, have non-functional mandibles, appendages and body attached to the pupal skin, and lose a degree of independent movement.

The pupae of some moths are able to wriggle their abdomen. The three caudal segments of the pupal abdomen (segments 8–10) are fixed; the other segments are movable to some degree. While the more evolved Lepidoptera can wriggle only the last two-three segments at the end of the abdomen, more basal taxa such as the Micropterigidae

Micropterigidae

can wriggle the remaining seven segments of the abdomen; this presumably helps them to protrude the anterior end from the pupal case before eclosion. The pupae of Hepialidae are able to move back and forth in the larval tunnel by wriggling, aided by projections on the back in addition to spines. Abdominal wriggling is considered to be of startle value and discouraging to predators. In the case of a few hawk moths

Sphingidae

, such as Theretra latreillii
Theretra latreillii
The Pale Brown Hawk Moth, Theretra latreillii, is a moth of the Sphingidae family. It is found in most of Asia, including Borneo, China, Hong Kong, the Philippines, Taiwan and also in the tropical regions of Australia....

, the wriggling of the abdomens is accompanied by a rattling or clicking sound which adds to the startle effect.

Defense and predation

Lepidopterans are soft bodied, fragile and almost defenseless while the immature stages move slowly or are immobile, hence all stages are exposed to predation

Predation

In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...

by birds, small mammals, lizards, amphibians, invertebrate predators (notably parasitoid

Parasitoid

A parasitoid is an organism that spends a significant portion of its life history attached to or within a single host organism in a relationship that is in essence parasitic; unlike a true parasite, however, it ultimately sterilises or kills, and sometimes consumes, the host...

and parasitic wasps and flies

Fly

True flies are insects of the order Diptera . They possess a pair of wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax...

) as well as fungi and bacteria. To combat this, Lepidoptera have developed a number of strategies for defense and protection which include camouflage

Camouflage

, aposematism

Aposematism

, mimicry, and the development of threat patterns and displays.

Camouflage is an important defense strategy enabled by changes in body shape, colour and markings. Some lepidopterans blend with the surroundings, making them difficult to be spotted by predators. Caterpillars can be shades of green that match their host plant. Others resemble inedible objects, such as twigs or leaves. The larvae of some species, such as the Common Mormon and the Western Tiger Swallowtail look like bird droppings.

Some species of Lepidoptera sequester or manufacture toxins which are stored in their body tissue, rendering them poisonous to predators; examples include the Monarch butterfly in the Americas and Atrophaneura
Atrophaneura
Atrophaneura, commonly referred to as the Red-bodied Swallowtails is a genus of butterflies in the Swallowtail family that are generally found in Asia.-Species:Listed alphabetically within groups:The latreillei species-group:...

species in Asia. Predators that eat poisonous lepidopterans may become sick and vomit violently, and so learn to avoid those species. A predator who has previously eaten a poisonous lepidopteran may avoid other species with similar markings in the future, thus saving many other species as well. Toxic butterflies and larvae tend to develop bright colours and striking patterns as an indicator to predators about their toxicity. This phenomenon is known as aposematism

Aposematism

.

Aposematism has also led to the development of mimicry complexes of Batesian mimicry

Batesian mimicry

Batesian mimicry is a form of mimicry typified by a situation where a harmless species has evolved to imitate the warning signals of a harmful species directed at a common predator...

, where edible species mimic aposematic taxa, and Müllerian mimicry

Müllerian mimicry

, where inedible species, often of related taxa, have evolved to resemble each other, so as to benefit from reduced sampling rates by predators during learning. Similarly, adult Sesiidae

Sesiidae

The Sesiidae or clearwing moths are family of the Lepidoptera in which the wings partially have hardly any of the normal lepidopteran scales, leaving them transparent. The bodies are generally striped with yellow, red or white, sometimes very brightly, and they have simple antennae...

species (also known as clearwing moths) have a general appearance that is sufficiently similar to a wasp

Wasp

The term wasp is typically defined as any insect of the order Hymenoptera and suborder Apocrita that is neither a bee nor an ant. Almost every pest insect species has at least one wasp species that preys upon it or parasitizes it, making wasps critically important in natural control of their...

or hornet

Hornet

Hornets are the largest eusocial wasps; some species can reach up to in length. The true hornets make up the genus Vespa and are distinguished from other vespines by the width of the vertex , which is proportionally larger in Vespa and by the anteriorly rounded gasters .- Life cycle :In...

to make it likely that the moths gain a reduction in predation by Batesian mimicry.

Eyespots

Eyespot (mimicry)

An eyespot is an eye-like marking. They are found on butterflies, reptiles, birds and fish. In members of the Felidae family , the white circular markings on the backs of the ears are termed ocelli, and they are functionally similar to eyespots in other animals.Eyespots may be a form of...

are a type of automimicry used by some lepidopterans. In butterflies, the spots are composed of concentric rings of scales of different colours. The proposed role of the eyespots is to deflect predators' attention. Their resemblance to eyes provokes the predator's instinct to attack these wing patterns. The role of filamentous tails in Lycaenidae has been suggested as confusing predators as to the real location of the head, giving them a better chance of escaping alive and relatively unscathed.

Some caterpillars, especially members of Papilionidae, contain an osmeterium

Osmeterium

The osmeterium is a fleshy organ found in the prothoracic segment of larvae of Swallowtail butterflies including Birdwings. This organ emits smelly compounds believed to be pheromones. Normally hidden, this forked structure can be everted when the caterpillar is threatened, and used to emit a...

, a Y-shaped protrusible gland

Gland

A gland is an organ in an animal's body that synthesizes a substance for release of substances such as hormones or breast milk, often into the bloodstream or into cavities inside the body or its outer surface .- Types :...

found in the prothoracic

Prothorax

segment of the larvae. When threatened, the caterpillar emits unpleasant smells from the organ to ward off the predators.

External links

SEM Image of butterfly scale and its pedicel (third from top).
Exquisite castaways – photo-feature on Lepidopteran eggs by National Geographic.
Uncommon vision – photo-feature on moths by National Geographic.

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

External morphology

General body plan

Distinguishing taxonomic features

Head

Antennae

Eyes

Palpi

Mouthparts

Thorax

Leg

Wings

Shape

Venation

Wing coupling

Scales

Structure

Colour

Function

Androconia

Abdomen

Genitalia

Development

Egg

Caterpillar

Chrysalis or pupa

Defense and predation

See also

External links